Apparatus and method for testing magnetic heads using translational slides and a rotatable arm

ABSTRACT

An apparatus for testing magnetic heads that interact with magnetic disks includes a translational slide and a rotatable arm mounted to one end of the slide. The translational slide moves the rotatable arm in a longitudinal direction parallel to the surface of a magnetic disk. The arm rotates the magnetic head to different positions relative to data tracks on the disk. A second translational slide moves the magnetic head vertically above the disk to adjust the vertical position of the head. The three movements of the head, (1)horizontally across the disk, (2)rotationally by the arm, and (3)vertically relative to the disk surface are controlled by servomechanisms. A read/write amplifier circuit is connected to the head under test. The test apparatus is controlled by a computer that interfaces with circuitry connected to the servomechanisms.

FIELD OF THE INVENTION

This invention relates to testing of magnetic disk drives and inparticular to testing of components related to magnetic disk drives,such as magnetic disks, magnetic heads and the like.

BACKGROUND OF THE INVENTION

A magnetic disk drive typically includes a stack of spaced apart,concentric magnetic disks mounted on a common spindle. Disposed adjacentto the stack of disks is an actuator arm assembly which comprises aplurality of arms extending into the spacings between the disks. Mountedon the distal end of each arm is a resilient load beam which in turncarries a magnetic head interacting with an associated magnetic disk.

FIG. 1 shows schematically a top plan view of a typical prior artmagnetic disk drive signified by reference numeral 2. The disk drive 2includes an arm 4 revolvable about an arm axis 6, and a magnetic disk 8rotatable about a spindle 10. There is a multiplicity of concentric datatracks 12 registered on the surface of the disk 8. Attached to *hedistal end of the arm 4 is an air bearing slider 13 carrying a magnetichead 14 which interacts with the magnetic disk 8. During normaloperation, the disk 8 spins at high speed in a rotational direction 15.The aerodynamics of the moving air between the slider 13 and the surfaceof the disk 8 provides sufficient buoyancy to suspend the slider 13above the disk surface. The height of the slider 13 above the disksurface is called the flying height of the magnetic head 14. To gainaccess to each data track 12, the arm 4 sweeps the head 14 in an arcuatelocus 16 traversing the disk surface.

Attention is now directed to the angle formed by the center line throughthe slider 13 and the tangent line to each data track 12. This angle isdefined as the skew angle of a particular data track. The tangent lineto the outermost track OD is labeled T_(OD), and the center line passingthrough the slider 13 is signified by reference numeral 18. The anglebetween the center line 18 and the tangent line T_(OD) of the outermosttrack OD is defined as the skew angle θ_(OD). Likewise, the anglebetween the center line 18 and the tangent line T_(ID) of the innermosttrack ID is defined as the skew angle θ_(OD). It should be noted thatthe skew angles θ_(OD) and θ_(ID) may be different in magnitude andpolarity, depending upon factors such as the arm length and relativeposition of the arm 4 with respect to the disk 8. With the center line18 as reference, the skew angle θ_(ID) is negative (measuredcounterclockwise) while the skew angle θ_(OD) is positive (measuredclockwise). With the arm axis 6 relatively far away from the spindle 10,the angle θ_(OD) is also smaller that the angle θ_(ID) in absolutevalue. For data tracks in between, the polarities and angular magnitudesrange between these extremes.

The skew angle is of significant importance in the design of a magneticdisk drive. To begin with, the skew angle dictates the angularorientation of the slider 13 with respect to the air stream while thedisk 8 is spinning in the direction 15. Accordingly, the dynamic airpressures exerted on the slider 13 are different at different datatracks. As a result, the slider 13 carrying the magnetic head 14 fliesat different heights above the disk surface at different skew angles.However, signal intensity sensed by the head 14 during the read mode, orwritten onto the disk 8 during the write mode, is a strong function ofthe flying height. Therefore, performance of the magnetic head 14 variesat different skew angles.

To compound the situation further, the radial distance of the magnetichead 14 away from the spindle center 20 also plays an important role inthe determination of the flying height. While the disk 8 is spinning,the outermost track OD experiences higher linear velocity relative tothe innermost track ID. Dynamic pressure exerted on the slider 13, alsoa function of linear velocity, is correspondingly higher at theoutermost track OD compared to the innermost track ID. In conjunctionwith the skew angle factors, the flying height of the magnetic head 14is indeed difficult to predict theoretically.

For the above reasons, in the design and manufacturing of magnetic diskdrives, there is a need for a tester which is capable of duplicating theskew angle and the radial distance of the magnetic head 14 in each ofthe data tracks 12 accurately.

Various disk drive testers have been proposed in the past. In U.S. Pat.No. 4,902,971, entitled "Magnetic Head and Disc Tester Employing PivotArm on Linearly Movable Slide", issued Feb. 20, 1990, a magnetic diskand head tester is disclosed. The tester includes an arm having aproximal end fixedly secured onto a translational slide, and a distalend attached with a magnetic head. To operate the tester, the skew angleof the outermost and innermost tracks need first be determined.Thereafter, the distance between the slide and the disk spindle, and theangular orientation of the arm are all correspondingly adjusted, suchthat the arm forms the predetermined skew angles at the outermost andinnermost tracks. The arm is then fixedly tightened onto the slide.Linear motion of the slide carrying the arm traversing the disk isutilized to simulate the rotational motion of the arm of a disk drive.Errors can be induced for data tracks located between the outermost andinnermost tracks. The situation would be more aggravated with smallerdisk drives having shorter arms which sweep arcs of smaller radii ofcurvature.

To rectify this problem, another tester has been proposed. In U.S. Pat.No. 5,254,946, entitled "Magnetic Head and Disk Tester with HeadCentrally Mounted on Radially-Moving, Rotatable Platform that SurroundsDisk", issued Oct. 19, 1993, the tester includes a testing arm fixedlyattached to a rotatable housing which is also capable of linearmovement. The disk under test is positioned underneath the housing andthe arm. Prior to usage, with the aid of a charged coupled device (CCD)camera, the magnetic head must first be manually and accurately alignedwith the center of rotation of the housing. Pretest preparation of thistype of setup is time consuming. Moreover, for the testing of differentdisks, considerable steps of mounting and demounting are involved.Testers of this type are not suitable for mass production environments.

Still, there are other testers employing X-Y manipulators to gain accessto the different data tracks on magnetic disks. Testers of this typeinvolve very complicated head traveling patterns and are not easy tooperate.

None of the prior art testers provide any features that are suitable forhigh throughput operation. There is a need for magnetic head and disktesters that can fulfill fast development turnaround and high volumeproduction requirements.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a magnetic head and disktester that is accurate, capable of switching to different testingsetups conveniently and swiftly, designed to involve minimal humanintervention and machine downtime, adaptable to interface a wide varietyof logic families, and suitable for high throughput operations.

Another object is to reduce testing costs in production and design ofmagnetic heads and disks.

The test apparatus of the present invention includes a rotational armhaving a proximal end pivotally mounted to a translational slide, and adistal end attached with a magnetic head. Both the arm and the slide areoperationally rotatable and slidable, respectively, above a tester base,thereby allowing the magnetic head to gain access to any location on amagnetic disk instantly and accurately.

In one embodiment, a magnetic head is attached to the distal end of thearm via a vertical slide which is installed at the arm's end and isslidable in a linear direction substantially vertical to the magneticdisk. The vertical slide can lift the magnetic head to any elevationabove the magnetic disk.

In another embodiment, a detachable module carrying the magnetic headand an amplifier circuit is releasably mounted to the vertical slide.This feature allows the magnetic head to be pre-wired before usage,thereby curtailing the tester downtime. Moreover, with the amplifierdisposed adjacent to the head on the detachable module, signal wiringdistance is reduced, thereby reducing the probability of noiseoccurrence.

Wiring the magnetic head having thin signal lead wires is normally atime-consuming and cumbersome process. In accordance with thisinvention, a novel rotary wire connector is installed on the arm tofacilitate this task. The wire connector includes a thumb wheel and aplurality of cams fixedly mounted on a common shaft adjacent to ahousing. Each cam is engaged to stretch a spring at a particularrotational angle of the shaft. While the spring is stretched, a thinwire can be inserted into the spring windings. When the thumb wheelrotates to other angles and the spring restores to its normallycompressed state, the wire is tightly trapped in the spring and makeselectrical connection.

The amplifier circuit linked to the magnetic head is also uniquelydesigned. The amplifier circuit comprises a data writing section and adata reading section. The data writing section includes a multiplierinterfacing with a linear current drive. Voltage levels of any logicfamilies are fully acceptable by the amplifier circuit. The multiplierscales down the input voltage levels before directing signals to thecurrent drive for current amplification. The linear current drive has awide linear range for reducing signal distortion. The data readingsection comprises at least one variable gain amplifier.

The testing apparatus of the invention is preferably computercontrolled. Servomechanisms can be installed to the rotational arm andthe translational and vertical slides for precise angle and distancemonitoring.

The testing apparatus is designed to be a self-contained testing systemrequiring minimal human intervention and is especially suitable forlarge testing throughput environment.

These and other features and advantages of the invention will beapparent to those skilled in the art from the following detaileddescription, taken together with the accompanying drawings, in whichlike reference numerals refer to like parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a disk drive having a rotatable armcarrying a magnetic head interacting with a magnetic disk;

FIG. 2 is an isometric view of the testing apparatus of the inventionillustrating the relative positions of the mechanical components;

FIG. 3 is a top plan view of the testing apparatus shown in FIG. 2,

FIG. 4 is a block diagram schematic showing the operational control ofthe testing apparatus of FIGS. 2 and 3;

FIG. 5 is a schematic showing the geometrical relationships between thetester components and the magnetic disk;

FIG. 6 is a flow diagram illustrating the algorithm used to direct themovements of the mechanical components of the testing apparatus shown inFIGS. 2-5;

FIG. 7 is a side plan view of the testing apparatus of FIG. 2 having thedisk stand and the linear servomechanism illustrated in ghost linesrevealing the translational slide and the calibration assembly;

FIG. 8 is an isometric view of a first embodiment of an assembledrotatable arm;

FIG. 9 is an exploded view of the rotatable arm shown in FIG. 8;

FIG. 10 is a magnetic head transfer assembly of the rotatable arm ofFIGS. 8 and 9 illustrating the wiring of the magnetic head;

FIG. 11 is a rear plan view of the magnetic head transfer assembly shownin FIG. 10;

FIG. 12 is an isometric view of a second embodiment of an assembledrotatable arm;

FIG. 13 is an exploded view of the rotatable arm shown in FIG. 12,illustrating a disengaged detachable module;

FIG. 14 is a exploded view of the detachable module shown FIGS. 12 and13 illustrating the relevant parts of the detachable module;

FIG. 15 is an isometric view of a rotary wire connector;

FIG. 16 is a top plan view of the rotary wire connector taken along line16--16 of FIG. 15;

FIG. 17 is a front plan view of the rotary wire connector taken alongline 17--17 of FIG. 15;

FIG. 18 is an end plan view of a plurality of cams mounted on the shaftof the wire connector of FIGS. 15-17;

FIG. 19 is a side plan view of a vertical slide of the testing apparatusof the invention;

FIG. 20 is a supplementary view taken from the dot-dash circleidentified as 20 shown in FIG. 19;

FIG. 21 is a block diagram schematic of the amplifier of the testingapparatus of the invention; and

FIG. 22 is a circuit schematic of the linear current drive and thevoltage feedback circuit shown in FIG. 21.

DETAILED DESCRIPTION OF THE INVENTION General Architecture

Reference is made to FIGS. 2 and 3 which show the testing apparatus ofthe invention generally signified by reference numeral 22. For the sakeof clarity in illustration, electrical wirings and circuit boards areremoved in FIGS. 2 and 3. The electrical aspects of the testingapparatus 22 will be described later in the specification.

The testing apparatus 22 includes a base 24 which comprises a rigidsurface. An example is a metal slab of sufficient rigidity andthickness. Alternatively, the base 24 can be equipped with shockabsorbing means (not shown).

On top of the base 24 is first translational means 26, such as atranslational slide 28 slidable on a stationary platform 27 in a lineardirection signified by reference numeral 30. The linear movement of theslide 28 is made possible by a stationary DC servo motor 35 driving alead screw 37 through the slide 28. A linear servomechanism 32, directlycoupled to the slide 28, is implemented for control of the linearmovement of the slide 28, via a feedback assembly 34.

Adjacent to the slide 28 but fixedly mounted to the stationary platform27 is a calibration assembly 29 having calibration screws 31A and 31Blocated at both ends. The calibration assembly 29 is installed for theinitial calibration of the linear servomechanism 32 prior to usage.

Pivotally attached to the translational slide 28 is a rotatable arm 36.There is another servomechanism 38 coupled to the rotatable arm 36 forcontrolling the rotational movement of the arm 36 in the rotationaldirection 40. The arm 36 includes a proximal end 42 which is pivotallymounted to the slide 28 through a shaft 44, and a distal end 46 which isaffixed with a magnetic head 48. Optionally, a counterweight 50 can beintegrally attached to the proximal end 42 of the arm 36 for the purposeof stabilizing the rotational movement 40.

Disposed between the magnetic head 48 and the distal end 42 of therotatable arm 36 is a second translational means or elevating means 52,such as a vertical slide 54 which is movable in a vertical direction 56(FIG. 2). The vertical slide 54 includes a servomechanism 55 whichallows the magnetic head 48 to be adjustably moved above the surface ofa magnetic disk 58.

A disk stand 60 is fixedly installed on the top of the base 24. The diskstand 60 comprises a stand base 62 carrying a revolvable spindle 64,which in turn is supporting the magnetic disk 58.

FIG. 4 is a block diagram showing the operational control of the testingapparatus 22. The main control is a computer generally designated by thereference numeral 66. The computer 66 can be a typical computer having aCPU 67 linked to a volatile memory, such as a RAM circuit 68 and anonvolatile memory, such as a hard disk 70. The CPU 67 is also tied to aperipheral interface circuit 72 which communicates with other circuitsexternal to the computer 66 via an interface data bus 88. Humaninteraction with the computer is made possible through a keyboard 74 anda video monitor 76.

As mentioned before, the key mechanical components of the apparatus 22are operationally movable during the testing process. Specifically,during testing, the slide 28 is freely slidable in the direction 30, therotatable arm 36 is freely rotatable in the direction 40, and thevertical slide 54 is movable in the direction 56 (FIGS. 2 and 3). Thedirections of movement 30, 40 and 56 are all controlled by therespective servomechanisms 32, 38 and 55, which in turn are controlledby the respective interface circuits 78, 80 and 82. There is also aread-write amplifier circuit 84 directly connected to the magnetic head48. The amplifier circuit 84 is controlled by the data interface circuit86 which is linked to the interface data bus 88.

The operation of the testing apparatus 22 requires a considerably lesserdegree of human adjustment and intervention than prior art testers. Forexample, during testing, variable data, such as the required skew anglesand the radial track distances, can be fed into the computer 66 throughthe keyboard 74. Specific testing routines can be loaded from thenonvolatile memory 70 into the RAM 68, and the required testingprocesses would be executed automatically by the CPU 67. The resultingtesting data sensed by the amplifier circuit 84 are sent back to the CPU67 via the data interface bus 88 for evaluation or for statisticalanalysis.

The following paragraphs describe the methods of operation and variouscomponents of the testing apparatus 22 in detail.

Principles of Operation

Reference is now directed to FIG. 5 which shows the geometricalrelationships of the translational slide 28 and the rotatable arm 36with respect to the magnetic disk 58. The operational movements of theslide 28 and the arm 36 of the testing apparatus 22 are hereindescribed.

Suppose the testing apparatus 22 needs to test a data track DD on themagnetic disk 58. In an actual disk drive, each data track ischaracterized by a skew angle a and a radial distance r, as explainedabove. To simulate the real disk drive operation, the testing apparatus22 must orientate the magnetic head 48 at the same skew angle α, andposition the head 48 at the same radial distance r away from the centerof the disk 19. However, the arm length A of the testing apparatus 22 isdifferent from the length of the real disk drive arm. Furthermore, thecenter of rotation 17 of the arm 36 of the tester 22 is possibly locateddifferently from that of the actual disk drive with respect to the diskcenter 19. The testing apparatus 22 of the invention solves theseproblems by automatically calculating the necessary translationaldistance y and the rotational angle θ, based on the given geometry, inconjunction with the required skew angle a and the radial distance r.Once the values y and θ are computed, the testing apparatus 22translates the slide 22 at the distance y and rotates the arm 36 at theangle θ and thereafter performs the testing.

In this embodiment, the calculations of the translational distance y andthe rotational angle θ are performed by the computer 66 (FIG. 4). Toequip the computer 66 for these tasks, two mathematical expressions mustfirst be derived, namely, the first and second expressions that definethe translational distance y and the rotational angle θ, respectively,as functions of the skew angle α, the radial distance r and the existentgeometrical arrangement.

FIG. 5 shows an exemplary arrangement of the slide 28 and the rotatablearm 36 with respect to the magnetic disk 58. For explanation purpose,this geometrical configuration is adopted for the followingillustration. From basic trigonometry and with reference to FIG. 5, thefollowing equations can be derived: ##EQU1## where: α=skew angle of themagnetic head with respect to the data track;

r=radial distance of the magnetic head to the center of the magneticdisk;

X=separation between the rotation center of the arm and the center ofthe magnetic disk along the x-direction;

d=distance between the rotation center of the arm and the center of themagnetic disk;

ψ=an arbitrary starting angle;

λ=angle between the line joining the centers of the arm of rotatationand magnetic disk with respect to the y direction;

R=the perpendicular distance from the center of the arm rotation to thetip of the magnetic head;

B=the perpendicular distance from the tip of the head to the line R;

A=the distance between the center of the arm rotation to the magnetichead; and

β, φ and γ are transitory angles.

Solving the eight simultaneous equations above, the translationaldistance y and the rotational angle θ can be expressed as follows:##EQU2##

Equation (9) now reduces to a function dependent upon the skew angle α,the radial distance r and the fixed geometrical parameters of theapparatus 22. Likewise, with the transitory angles β equation (11)! andλ equation (12)! substituted into it, equation (10) also depends on theskew angle α, the radial distance r and the fixed geometrical parametersof the apparatus 22. Equations (9)-(12) can be programmed into thecomputer 66. Once the skew angle α and the radial distance r areentered, the computer 66 would calculate the sought after values y and θautomatically.

FIG. 6 is a flow chart illustrating the algorithm used by the computer66 to direct the testing apparatus 22 for the testing of each datatrack.

The flow chart of FIG. 6 can best be explained in accompany with theoperational schematic of FIG. 4. Prior to any testing as shown in block21A, equations (9)-(12) are programmed into the RAM circuit 68, eithervia the nonvolatile memory 70 or manually via the keyboard 74. Then theCPU 67 asks for whether the testing is for a new head or a disk as shownin the decision block 21B. If the answer is negative, the testingprocess proceeds to block 21C which requests for the skew angle a andthe radial distance r. Thereafter, the CPU 67 calculates thetranslational distance y from the mathematical function y=f(α,r), whichin essence is the equation (9), as shown in block 21E. The calculationof the rotational angle θ also follows as shown in step 21F. Themathematical function used this time is θ =g(α,r) which basicallyincludes equations (10)-(12). Based on the computational result of block21E, the CPU 67 directs the motor interface circuit 206 via theinterface data bus 88 to advance the translational slide 28 a distancey, as shown in block 21G. In a similar manner, from the calculatedresult of block 21F, the CPU 67 instructs the motor interface circuit211 to rotate the rotatable arm 36 an angle θ, as shown in block 21H.When the magnetic head 48 attains the proper arm translational distancey and the arm rotational angle θ corresponding to the correct skew angleθ and radial distance r of an actual disk, the apparatus 22 can performthe test as shown in step 21J.

Returning now to block 21B in FIG. 6, suppose a new disk or head needsto be tested. The new disk or head is simply mounted onto the apparatus22. New parameters such as the relative positions or dimensions of thenew head or disk are entered into the computer 66 as shown in block 21D.The testing then proceeds and continues to block 21C as previouslydescribed. It should be emphasized that by virtue of calculating thetranslational distance y and the rotational angle θ via mathematicaltransformation of multiple variables α and r in advance of movements,the arm 36 and the slide 28 can rotate and move with flexibility andagility. This is in sharp contrast with most prior art testers, such asthe tester disclosed in the aforementioned U.S. Pat. No. 5,254,946,where the movement algorithms associated with the rotatable housing areone dimensional. That is, the magnetic head translates and rotatessolely as a function of the radial distance or skew angle, respectively,but not both. As a consequence, designs of this type places considerablerestriction the mobility of the movable parts. This partly contribute tothe substantial mounting and dismounting involvement during diskchanges, and the stringent head alignment requirement prior to testing.

The testing apparatus of the invention involves no such inconvenience.

The Translational Slide

Shown in FIG. 7 is a side plan view taken along line 7--7 of FIG. 2. Thedisk stand 60 and the linear servomechanism 32 are shown in phantomlines, thereby revealing first translational means 26 unobstructed.

With reference to FIGS. 3 and 7, first translational means 26 in thisembodiment includes a slide 28 slidably disposed atop the stationaryplatform 27. There is a trough 92 (FIG. 3) having a pair of guide rails90A and 90B upon which the slide 28 is slidably resting. Partiallyembedded inside the guide rails 90A and 90B is a plurality of ballbearings 94 which facilitate the linear movement 30 of the slide 28.

The linear movement of the slide 28 in the direction 30 is achieved by aDC servo 35 driving the lead screw 37 which engages the slide 28 througha nut 96 attached to the slide 28. The servo motor 35 is fixedlyattached to a bracket 98 which in turn is permanently anchored onto thestationary platform 27. The bracket 98 is shown partially fragmentary toreveal a flexible coupler 100 connecting the motor shaft 102 and thelead screw 37. The flexible coupler 100 corrects misalignment, reducesvibrations and enables a smoother rotational movement of the lead screw37 at the distal end inside the slide 28. There are also ball bearings104 encompassing the lead screw 37 to assist the rotational movement. Asarranged, when the motor 35 is energized, the lead screw 37 spins alongwith the coupler 100 and the motor shaft 102. The screw 37 engaging thenut 96 drives the slider 28 along the linear direction 30. The slide 28illustrated in hidden lines shown in FIG. 7 portrays an alternativeposition of the slide 28 glided along the rails 90A and 90B.

Atop the slide 28 is an extension plate 106 (FIG. 7) which is attachedto the rotational servomechanism 38. The extension plate 106 is boltedonto the slide 28 via bolts 108A-108F. Likewise, the rotationalservomechanism 38 is bolted onto the extension plate 106 through bolts110A and 110B (FIG. 3).

The rotational servomechanism 38 and the rotatable arm 36 are connectedtogether through the shaft 44. The motor (not shown) inside therotational servomechanism 38 carries and moves the arm 36 in therotational direction 40 (FIG. 3). Arranged in this manner, the magnetichead 48 affixed to the distal end 46 of the arm 36 can traverse themagnetic disk 58 on the top of the disk stand 60.

The linear feedback assembly 34 is fixedly attached to the sidewall ofthe slide 28. The feedback assembly 34 includes a laser reflector 112and a reference extension 114. The calibration assembly 29, havingcalibration screws 31A and 31B, are also fixedly outrigged onto thestationary platform 27. The reflector 112, the extension 114, thecalibration assembly 29 with the screws 31A and 31B are installed forthe purpose of calibrating the servomechanism 32 prior to usage.

The Rotatable Arm

FIGS. 8 and 9 show a first embodiment of the rotatable arm 36 in furtherdetail. FIG. 8 is an assembled drawing of the arm 36 and FIG. 9 is anexploded view showing the relevant parts made up of the arm 36. The arm36 includes an arm body 116 having a proximal end 42 and a distal end46. At the proximal end 42 is integrally attached a shaft coupler 118,which is coupled to a motor (not shown) inside the rotationalservomechanism 38 for rotational movement. Optionally, a counterweightportion 50 can be integrally annexed to the proximal end 42 of the arm36 to effectuate more balanced rotational movements.

There are two flanges 120A and 120B integrally formed with the arm body116. As shown in FIGS. 8 and 9, the upper flange 120A is mounted to alead screw housing 122 which encompasses a lead screw 126. The leadscrew 126 has one end engaging the vertical slide 54 and another endconnected to a stepper motor 124. When the motor 124 is activated, themotor 124 spins the lead screw 126 which in turn drives the verticalslide 54 along the vertical direction 56. The magnetic head 48, beingaffixed to the vertical slide 54, moves along with the slide 54 in thedirection 56. It should be appreciated that another slide, similar tothe vertical slide 54, can also be assembled onto the lower flange 120Bin a similar fashion carrying another magnetic head, such that twomagnetic heads can interact with a double-sided magnetic disk.

At the distal end 46 of the arm 36 and on the vertical slide 54 is arelease mechanism 128, which is installed for accommodating a headtransfer assembly 130. The release mechanism 128 comprises a lever 132pivoted about a lead screw 126 behind a slide block 134. To lock thehead transfer assembly 130 into position, the assembly 130 is firstplaced in the reserved slot 136 (FIG. 9). The lever 132 is then pulledupwardly in the direction 138, thereby advancing the lead screw 126 andthe slide block 134 toward the head transfer assembly 130. The tip ofthe screw (not shown) then penetrates into the opening 140 of theassembly 130, and coupled with the compressive force of the slide block134 against the assembly 120, the head assembly 120 is tightly securedin place.

The read-write amplifier 84 can be proximally disposed adjacent to thehead transfer assembly 130, such that sensed signals detected by themagnetic head 48 are amplified first before sending signals to othercircuitries over a long distance for processing. In this embodiment, theamplifier circuit 84 is screwed onto the front part of the verticalslide 54. Arranged in this manner, the chance of noise contamination onthe preliminarily sensed signal is substantially reduced. Optionally,other circuits, such as a high frequency buffering circuit 142, can besecured to the arm body 116 via screws 144A and 114B, and connectors146A and 146B.

Modern day magnetic heads are fabricated at a miniaturized scale.Magnetic heads must also electrically communicate with other circuitsdisplaced at a distance from the head in a tester. However, the wiresleading to the magnetic heads are normally exceedingly small indiameter. Handling such wires in setting up the testing processes is atime-consuming and cumbersome endeavor.

FIGS. 10 and 11 show the wiring of the magnetic head 48 on the headtransfer assembly 130. Normally, a magnetic head 48 comprises a slider148 carrying at least one transducer 150 at the slider edge. In aninductive head, only two wires would come out of the head 48. In amagnetic head with both inductive and magnetoresistive elements, fourwires would emanate from the head 48 ready for wiring. In thisembodiment, the wires 152 sourcing out from the head 48 are solderedonto small paddle boards 154 which are insertable into receptacles 156.There are internal wirings inside the head transfer assembly 130 leadingto pogo pins 158 (FIG. 11), which are in turn insertable onto a smallprinted circuit board on the floor of the slot 136 in the vertical slide54 (FIG. 9).

To further curtail manual intervention and reduce tester downtime, amodular approach for component connectivity is adopted. FIGS. 12-14 showa second embodiment of the rotatable arm signified by reference numeral36'. FIG. 12 is an assembled drawing of the arm 36' and FIGS. 13 and 14are exploded views showing the relevant parts made up of the arm 36'.

As with the rotatable arm 36 of the first embodiment, the shaft coupler118 is integrally affixed to the arm body 116 and the arm 36' has adistal end 46 and a proximal end 42. Optionally, a counterweight portion50 can be joined to the proximal end 42 of the arm 36, for the purposeof balancing the rotational movement.

There are two flanges 120A and 120B integrally formed with the arm body116. Shown in FIGS. 12-14 is the upper flange 120A attached to a leadscrew housing 122 which encompasses a lead screw 126. The lead screw 126has one end engaging a vertical slide 54' and another end connected to astepper motor 124. When energized, the rotational movement of thestepper motor 124 spins the lead screw 126, which in turn drives thevertical slide 54' in a linear movement along the vertical direction 56.It should be appreciated that another similar vertical slide, similar tothe slide 54', can also be assembled onto the lower flange 120B in asimilar fashion carrying another magnetic head, such that two magneticheads interact with a two-sided magnetic disk.

The distinctive feature of the arm 36' of this embodiment compared tothe arm 36 of the previous embodiment is a detachable module 160 whichis herein described.

The Detachable Module

FIG. 13 shows the detachable module 160 that is releasably attached tothe distal end 46 of the rotatable arm 36'. There is a pair of handgrips 162A and 162B pivotally and resiliently attached to the module160, which grips allow the module 160 to be releasably insertable ontothe vertical slide 54'.

FIG. 14 is an exploded view of the detachable module 160, exposing theconstituent parts in additional detail. The module 160 includes a modulebase 164 having hand grips 162A and 162B, and a pair of anchoring pins166A and 166B (only one is shown in FIG. 14) insertable into therespective openings 169A and 169B formed in the vertical slide 54'. Atopthe module base 164 are an amplifier board 84', and a head transferassembly 130'. In this embodiment, the amplifier board 84' is attachableonto the module base 164 through a plurality of connector pins 168insertable into openings 170 formed in the base 164. On the other hand,the head transfer assembly 130' is secured onto the base 164 via screws172. The magnetic head 48 is securely latched under the head transferassembly 130' via a grip (not shown) controlled by a lever 167. There isalso a rotary wire connector 174 disposed on the top of the amplifierboard 84' via soldering or screws. The fully assembled detachable module160 is as shown in FIG. 12.

The advantage of integrating the components in the form of a module ismultifold. To begin with, tester downtime is significantly reduced. Themodule 160 can be prepared and pre-wired before snapping onto thevertical slide 54'. There is no need to shut down the tester formagnetic head wiring, for example. In the event of repair ormaintenance, the module 160 can be separately released without affectingthe rest of the testing setup. Another pre-wired module 160 may beinserted as a replacement. The amplifier circuit 84' can be placed veryclose to the magnetic head 48 within the module 160. There is no need toextend long wirings from the magnetic head 48 to the amplifier circuit84', thereby reducing the probability of noise occurrence.

It should be appreciated that in a production environment, a largequantity of magnetic heads or disks need to be tested and turned overwithin a short period of time. To aggravate the matters further, thereare varieties of heads and disks of different sizes and specifications.With most prior art testers, considerable mounting, demounting andwiring steps are involved for change of test setup. The modular approachof preparing the tester in the present invention substantiallyfacilitates the testing process.

The Rotary Wire Connector

The rotary wire connector 174 shown in FIGS. 12-14 is a device which isdesigned to alleviate the normally cumbersome wiring process.

Shown in FIG. 15 is an enlarged perspective view of the connector 174.FIGS. 16 and 17 are top and side views taken along line 16--16 and17--17 of FIG. 15, respectively. The wire connector 174 comprises ahousing 176 having a plurality of wire openings 178A-178D. Springs180A-180D are disposed inside the wire openings 178A-178D, respectively.Atop the housing 176 are a plurality of cams 182A-182D attached througha common shaft 180. The shaft 180 passes through sleeves 184A and 184B(FIG. 16) integrally joined to the housing 176. At one end of the shaft180 is a thumb wheel 186 having indicating labels 188 marked thereonalong the cylindrical wheel wall. At the other end of the shaft is alocking wheel 190 having a plurality of hemispherical cavities 192 onthe cylindrical wheel wall. When the shaft 180 is rotated through thethumb wheel 186, the cavities 192 of the locking wheel 190 engage a ballbearing 194 and a spring 196 inside the housing 176 (FIG. 17), therebyenabling the shaft 180 to rotatably move in discrete steps.

At the top of the housing 176 is a plurality of slots 198A-198Daccommodating a plurality of piano keys 200A-200D, respectively. Thepiano keys 200A-200D are pivotally attached though a common pin 202inside the respective slots 198A-198D. For each of the piano keys200A-200D, one end is pressed against one of the cams 182A-182D, and theother end is attached to one of the compression springs 180A-180D.

FIG. 18 is an end view of the shaft 180 passing through the eccentriccams 182A-182D. When the thumb wheel 186 is rotated, the shaft 180 turnsthe eccentric cams 182A-182D simultaneously. The cams 182A-182D compressthe piano keys 200A-200D one at a time, and accordingly stretch thecompression springs 180A-180D one at a time, respectively. While each ofthe springs 180A-180D is stretched, bare wires can be inserted intospring windings in the respective openings 178A-178D for makingelectrical connections. The labeling 188 on the thumb wheel 186indicates which of the springs 180A-180D is stretched, therebyfacilitating the process of wiring. When none of the springs arestretched, all the wires would be tightly trapped in place. With thisarrangement, wiring of the thin wires associated with a magnetic head isno longer a time consuming or cumbersome task.

There is also a plurality of paddle board openings 204A-204D formed inthe housing 176. As an alternative, paddle boards linking to themagnetic head wires can be inserted into the openings 204A-204D, in lieuof the bare wire trapping in the springs 180A-180D. There are no fixturechanges at all to make the transition.

The Translational and the Rotational Servomechanisms

With reference to FIGS. 3 and 4, there are two servomechanisms, namely,the linear servomechanism 32 and the rotational servomechanism 38guiding the linear movement of the slide 28 and the rotationaldisplacement of the arm 36, respectively. In the preferred embodiment,the servomechanisms 32 and 38 are respectively Model 3070 and Model 3035servo positioning systems manufactured by CMX corporation ofWallingford, Connecticut.

Both servomechanisms 32 and 38 utilize the wavelength of light emittingfrom the respective coherent light sources as the basis of displacementmeasurement. Specifically, the servomechanisms 32 and 38 employ opticalinterferometers. The principle of operation of the opticalinterferometers is herein briefly described. As shown schematically inFIG. 3, inside the housing of the servomechanism 32, a Helium Neon(HeNe) laser diode L emits a coherent light with wavelength ofapproximately 810 nm (nanometers) along a path P1 toward an internallight splitter S. The light splitter S is essentially a partiallysilvered mirror allowing half of the light to pass through, that strikesan internal mirror Ml along a path P2 and reflects the other half whichheads toward an external mirror M2 located inside the reflector 112along a path P3. The split light rays are reflected. The reflected lightrays from the mirrors M1 and M2 at the same time are directed toward atarget T along the paths P4 and P5, respectively. As a consequence, alight interference pattern is formed on the target T which is an arrayof charge coupled devices. Different distances d of the mirror M2disposed away from the servomechanism 32 generate different interferencepatterns on the target T. Since the mirror M2 is fixedly attached to theslide 28, the precise location of the slide 28 along the stationaryplatform 27 can be ascertained by interpreting the interference patternon the target T.

Prior to usage, the servomechanism 32 needs to be calibrated. Thecalibration assembly 29 having the two lead screws 31A and 31B performsthis duty. To begin with, the desired "home position" of the slide 28must first be determined. This is accomplished by first turning thescrew 31B to a location intended as the home position. The calibrationextension 114 (also shown in FIG. 7) is then moved toward thecalibration screw 31B until the extension 114 is in contact with the tipof the screw 31B. However, the extension 114 is fixedly attached to theslide 28. Therefore the slide 28 must also move along with the extension114 to the home position. This position is then registered into thecomputer 66 as the designated home position.

Next, the "end position" of the slide 28 needs to be determined. This isachieved by placing a calibration block (not shown) of predeterminedfixed length F between the tips of the screws 31A and 31B. The block isnormally made of a material which is temperature compensated. That is,the coefficient of thermal expansion of the calibration block does notvary much over the operational temperature range. The screw 31A is thenadjusted until both screws 31A and 31B snugly clamp the calibrationblock. Thereafter, the calibration block is removed. The slide 28 thenadvances toward the screw 31A until the calibration extension 114 is incontact with the tip of screw 31A. This position is then registered intothe computer 66 as the end position of the slide 28.

With the home and end positions determined, any distance along the fixeddistance F can be located via the calibrated servomechanism 32. Duringnormal operation, suppose the slide 28 needs to be positioned at acertain distance along the fixed distance F. That distance is firstregistered as an input in the computer 66. The CPU 67 of the computer 66directs the motor interface circuit 206 to advance the lead screw 37 acalculated number of revolutions (FIG. 4). Thereafter, the calibratedservomechanism 32 checks the advanced distance of the slide 28, in amanner as described above, against the inputted distance value. Shouldthere be any discrepancies between the two values, the servomechanism 32requests the CPU 67 to provide necessary corrections via thetranslational servomechanism interface circuit 78. The above describedprocess repeats itself several times until an acceptable displacementtolerance is reached. In the preferred embodiment, the resolution ofdisplacement of the slider 28 is accurate within a range of 6.33 nm.

With regard to the rotational servomechanism 34, the principle ofoperation is similar except rotational displacements are used togenerate light interference patterns. Moreover, the calibration assemblyin the form of angular internal stops is located inside the housing.Once the angular home position is determined, the rotationalservomechanism 34 can be operated in the same manner as the linearservomechanism 32 as described above. For the sake of conciseness, theoperational detail of the rotational servomechanism 34 is not furtherelaborated. The angular resolution of the rotatable arm in the preferredembodiment is accurate within a range of 0.125 μradians.

The Z-Height Adjustment Mechanism

Another servomechanism is implemented in the testing apparatus 22 of theinvention. FIG. 19 shows a side plan view of the distal end 46 of therotatable arm 36. As described before, the lead screw housing 122 isfixedly attached to the flange 120A which is stationary with respect thearm body 116. At the top of the housing 122 is the stepper motor 124which drives the lead screw 126 inside the housing 122. The lead screw126 engages a nut 212 held by a bracket 214 fixedly secured on the backside of the vertical slide 54. By virtue of spinning the screw 126, thestepper motor 124 is capable of driving the vertical slide in a verticaldirection 56 relative to the arm body 116.

There is a sensor finger 214 integrally extended from the vertical slide54. The sensor finger 214 follows the up-down motion 56 of the verticalslide 54 while the motor 124 is actuating the screw 126. FIG. 20 is asupplementary view taken from the dot-dash line circle identified as 20shown in FIG. 19, showing the tip portion of the sensor finger 214 andthe magnetic head 48 at a larger scale.

As shown in FIG. 20, near the distal end of the sensor finger 214 is adielectric layer 216 sandwiched between the bottom surface of the finger214 and a thin layer of conducting metal 218. The magnetic disk 58 isbasically made of metal and is normally tied to ground potential. Thethin metal layer 218 and the surface 220 of the magnetic disk 58 form anelectrical capacitor with the metal layer 218 and the disk surface 220acting as capacitor electrodes. As is well known in the art, capacitancevalue is inversely proportional to the distance between the electrodes.In the present case, the electrode distance is the displacement of themetal film 218 with respect to the disk surface 220. This distance isdefined as the Z-height Z of the tester 22.

The Z-height Z should be distinguishable from the flying height h of theslider 148 above the disk surface 220. The flying height h of the slider148 is dependent upon a number of aerodynamic parameters while the disk58 is in spinning motion. However, the flying height h is related to theZ-height Z, which is essentially an arbitrary fixed reference point atthe vertical slide 54 with respect to the disk surface 220. In thepreferred embodiment, the Z-height Z is defined as the distance betweenthe sensing metal film 218 and the disk surface 220.

To understand the feedback mechanism of the vertical slide 54, attentionis now directed back to FIGS. 4 and 19. As with the translationalservomechanism 32, a home position as reference needs first to bedesignated. Once the home position is determined, any distance above thedisk surface 220 can be ascertained by evaluating the capacitance valueformed between the metal film 218 and the metal disk 58. For example,suppose the vertical slide 54 needs to be positioned at a certaindistance above the disk surface 220. This distance is fed into thecomputer 66. The CPU 67 of the computer 66 directs the motor interfacecircuit 220 to activate the motor 124 which in turn spins the lead screw126 a calculated number of revolutions. Simultaneously, the lead screw126 engages the nut 212 and moves the vertical slide 54 to the intendeddistance above the disk surface 220. Then, the Z-height servomechanisminterface circuit 82 checks the capacitance value of the metal film 218and the disk 58 at that particular location, and thereafter translatesthe capacitance value into a linear distance. Should there be anydiscrepancies between the inputted value and the detected value, theservomechanism 82 requests the CPU 67 to provide necessary correctionsvia the motor interface circuit 220. The above described process repeatsitself several times until an acceptable tolerance is reached. In thepreferred embodiment, the resolution of displacement of the verticalslider 54 is accurate within a range of 6.33 nm.

The Amplifier Circuit

FIG. 21, which is an electrical block diagram of the amplifier circuit84 or 84' mentioned previously, depicts the amplifier circuit 84 or 84'that can be partitioned into an inductive head circuit portion 224 and amagnetoresistive (MR) head circuit portion 226. Either one or all of thecircuit portions 224 and 226 can be used during normal operationdepending on applications.

The inductive head circuit portion 224 can be further divided into adata writing section 228 and a data reading section 230. The datawriting section 228 includes a multiplier 232 driving a linear currentdrive 234 which is linked to an inductive head 236 through a pluralityof switches 238A-238D. There is also a voltage feedback circuit 240provided for output stabilization. The feedback circuit is coupledbetween the inductive head 236 and the linear current driver 234. Thedata reading section 230 includes a variable gain amplifier 242 tied tothe inductive head 236.

The magnetoresistive head circuit portion 226 comprises another variablegain amplifier 244 connected to an MR head 246. There is also a biascurrent source 248 attached to the MR head 246 to provide bias currentto the head 246 for orienting the head 246 into the proper operatingregion.

In the preferred embodiment, the multiplier 232 is a discrete componenthaving a part number AD834, manufactured by Analog Devices, Inc. ofWilmington, Mass. The variable gain amplifier 242 is another discretecomponent having a part number NE/DA5209, manufactured by PhilipsSemiconductor of Eindhoven, the Netherlands. The detailed schematic ofthe linear current driver 234 and the voltage feedback circuit 240 areshown in FIG. 22. These two circuits are herein depicted along with theoperational description of the inductive head circuit portion 224.

With reference to FIG. 21, during the data writing process, theread/write select input R/W is first activated. A high signal applied atthe input R/W closes electrical switches 238A, 238C, 238E and 238H.Write data in true and complementary versions are then applied to thewrite data input WD and the write data complementary input WD,respectively. optionally, only the true version of the write data, thatis, without the complementary version, can be supplied to the multiplier232. At the same time, a DC voltage level is also tied to the writecontrol input WC. As is well known in the art, a multiplier acceptsmultiple input signals and generates output signals as a product of thecorresponding input signals. In this case, the output voltages V_(O) andV_(CO) of the multiplier 232 are made available at nodes 250 and 252,respectively, in accordance with the following equations:

    V.sub.O =K×V.sub.WD ×V.sub.Wc                  (13)

    V.sub.CO =-(K×V.sub.WD ×V.sub.WC)              (14)

where V_(WD) and V_(WC) are the voltages at the inputs WD and WCrespectively, and K is a multiplier constant which is a function of thecircuit parameters of the multiplier circuit 232 and is adjustable. Anytype of logic levels, irrespective of whether the input signals areEmitter-Coupled Logic (ECL) or Transistor-Transistor Logic (TTL), can beapplied to the amplifier circuit 84 or 84' via the inputs WD and WD. Thereason is because the DC voltage level at the write control input WC canscale the input signals via the multiplier 232 in accordance with theabove mentioned equations (13) and (14) into proper voltage levels atthe multiplier outputs 250 and 252 before processing.

FIG. 22 shows the internal structures of the linear current drive 234and the voltage feedback circuit 240. The linear current drive 234 isessentially a differential amplifier 254 having an assertive circuitportion 255 which includes a transistor Q4, and a complementary circuitportion 257 which comprises a transistor Q5. A first voltage referencesource 256, having a transistor Q1 and the resistors R1 and R2, is alsoinstalled adjacent to the differential amplifier 254. Current flowingthrough resistors R1 and R2 and the base-emitter junction of thetransistor Q1 establishes a fixed voltage at the emitter node 258 of thetransistor Q1. As a result, the voltage levels at the base-emitterjunctions of transistors Q2 and Q3 are also fixed, yielding fixedcollector currents I1 and I2, respectively. It should be noted that incontrast to most prior art amplifier circuits where only one currentsource is provided for the crosscoupled transistors in the differentialamplifier, transistors Q2 and Q3 here act as dual current sources,namely, first and second current sources 259 and 261. Currents I1 and I2from the first and second current sources 259 and 261, respectively,will proportionally steer into the transistors Q4 and Q5, depending onthe respective base-emitter voltages of these two transistors. Thisfeature of having double current sources 259 and 261 significantlyincreases the linear amplification range of the current drive 234.

Reference is now directed to the differential amplifier 254 in which thebase-emitter voltages of the transistor Q4 and Q5 are controlled by themultiplier outputs 250 and 252 through emitter follower transistors Q6and Q7, respectively. For the purpose of illustration, suppose thevoltage at node 250 is low, and the complementary voltage at node 252 ishigh, the voltages at nodes 262 and 260 would follow the voltages atnodes 250 and 252 with the corresponding base-emitter junction drops oftransistors Q6 and Q7, respectively. With the voltage potential at thebase of transistor Q5 lower than that of the transistor Q4, thetransistor Q5 is more actively turned on in comparison to the transistorQ4. Consequently, in addition to the current I2, a portion of thecurrent I1 flows into transistor Q5 through the bridge resistor R3. Themerged current is available as write current I3 passing to the magnetichead. However, the other current I4 associated with the magnetic head issinking into the voltage feedback circuit 240.

In the voltage feedback circuit 240, there are a second voltagereference source 264 comprising a transistor Q8 and resistors R4 and R5,and a third voltage reference source 266 including a transistor Q9 andresistors R6 and R7. In a similar manner as the first voltage referencesource 256, the voltages at the base-emitter junctions of transistorsQ10 and Q11 are also determined by the emitter voltages of thetransistors Q8 and Q9, respectively, yielding corresponding collectorcurrents I5 and I6, respectively. However, the voltage potentials at thebases of the transistors Q8 and Q9 are not constant. Instead, these basepotentials are dependent on the outputs of the first and second feedbackamplifier stages 268 and 270, respectively, which are in turn driven bythird and fourth feedback amplifier stages 272 and 274, respectively.

Returning now to the example illustrated above, with current driven outof the linear current driver 234 into the inductive head 236 (shown inFIG. 21), there is an ohmic drop across the inductive head 236. Theohmic drop is sensed by the third and fourth amplifier stages 272 and274, respectively, at nodes 276 and 278. If the current driving out ofthe current driver 234 is I3, the voltage potential at the node 276 ishigher in value than the voltage potential at the node 278. Afterpassing the amplifier stages 268, 270, 272 and 274, the voltagepotential at the base of the transistor Q9 would be driven higher invalue in comparison to the voltage potential at the base of thetransistor at Q8 as a result. After the emitter follower actions, thevoltage potential at the base of the transistor Q11 is consequentlyhigher in value than the corresponding base voltage potential for thetransistor Q10. The transistor Q11 is therefore more actively turned onthan the transistor Q10. That is, the collector current I6 is higherthan the collector current I5. Therefore, the current direction for I4shown in FIG. 22 should be reversed, or alternatively, the current valueof the current I4 is negative. These push and pull actions of thecurrents I3 and I4 constitute the write current injecting into theinductive magnetic head 236 (FIG. 21). The voltage feedback circuit 240also serves the regulating function of stabilizing the write currentinto the inductive magnetic head 236. The degree of feedback can bepredetermined by adjusting the ohmic values of the resistors R11 and R12in the third amplifier stage 272, and R13 and R14 in the fourthamplifier stage 274.

Variations of the Preferred Embodiment

The testing apparatus of the present invention provides the advantagesof allowing fast testing setup changes and adjustments, minimizing humanintervention and machine downtime, and equally as important, accuracy.All are of critical importance to production environments requiring hightesting throughput.

Finally, other variations are possible within the scope of theinvention. For example, the servomechanisms 32 and 38 need not beoptical interferometers. Other feedback mechanisms, such as systemsemploying acoustics, can well be used as substitutes. The verticalservomechanism 52 need not be the type involving capacitance sensing. Asan alternative, an optical interferometer can take its place. Thedetachable module 160 need not be releasably latched onto the verticalslide 54' through hand grips 162A and 162B. The detachable module 160can well be attached to the vertical slide by other methods such asthrough screws, fastening or various other latching mechanisms. The cams182A-182D can be fully encased within the housing 176. Moreover, thecams 182A-182D need not be circular, and the cams can have other shapessuch as elliptical. In the current drive circuit 234 and the voltagefeedback circuit 240 of the amplifier circuit 84 or 84', other types oftransistors, such as complementary-metal-oxide-silicon (CMOS)transistors, can replace the bipolar transistors with minor circuitmodification. These and other changes in form and detail may be madetherein without departing from the scope and spirit of the invention asdefined by the appended claims.

What is claimed is:
 1. A testing apparatus for testing components of adisk drive including a magnetic head that interacts with a magnetic diskwhich includes a plurality of concentric data tracks magnetized thereoncomprising:a base; translational means disposed above said base, saidtranslational means being slidable in a longitudinal directionsubstantially parallel to the surface of said magnetic disk; a rotatablearm having a distal end attached to said magnetic head, and a proximalend pivotally connected to said translational means; wherein saidtranslational means and said rotatable arm respectively areoperationally slidable and rotatable above said base, such that duringtesting, while accessing different data tracks on said magnetic disk,said translational means slides said rotatable arm and causes saidmagnetic head to rotate to different positions relative to the datatracks on said magnetic disk; and elevating means slidably connected tosaid distal end of said rotatable arm, said elevating means beingslidable in a direction other than said longitudinal direction andsubstantially vertical to the surface of said magnetic disk, whereinsaid magnetic head is connected to said distal end of said rotatable armby said elevating means, thereby allowing said elevating means toadjustably move said magnetic head relative to said magnetic disk. 2.The testing apparatus as set forth in claim 1 wherein said translationalmeans further includes linear feedback means for allowing saidtranslational means to adjustably move said rotatable arm along saidlongitudinal direction.
 3. The testing apparatus as set forth in claim 2wherein said linear feedback means includes an optical interferometer.4. The testing apparatus as set forth in claim 1 wherein said rotatablearm includes rotational feedback means for allowing said rotatable armto adjustably rotate said magnetic head above said magnetic disk.
 5. Thetesting apparatus as set forth in claim 4 wherein said rotationalfeedback means includes an optical interferometer.
 6. The testingapparatus as set forth in claim 1 wherein said elevating means includeslinear feedback means for allowing said elevating means to adjustablymove said magnetic head relative to said magnetic disk along a directionsubstantially vertical to the surface of said magnetic disk.
 7. Thetesting apparatus as set forth in claim 6 wherein said linear feedbackmeans includes capacitance sensing means.
 8. The testing apparatus asset forth in claim 1 comprising a detachable module, having a modulebase, releasably attached to said distal end of said rotatable arm,wherein said magnetic head is attached to said rotatable arm via saiddetachable module, a magnetic head transfer mount disposed on saidmodule base having said magnetic head attached thereto, and disposed onsaid module base, and an amplifier circuit proximally disposed adjacentto said transfer mount.
 9. The testing apparatus as set forth in claim 8wherein said amplifier circuit comprises a write data circuit, includinga multiplier, and a current driver having input terminals connected tosaid multiplier and output terminals connected to said magnetic head.10. The testing apparatus as set forth in claim 9 wherein said currentdriver includes a feedback circuit connected thereto for signalstabilization.
 11. The testing apparatus as set forth in claim 9 whereinsaid amplifier circuit comprises at least one read data circuit,including a variable gain amplifier.
 12. The testing apparatus as setforth in claim 8 wherein said detachable module includes a wireconnector which comprises:a housing; at least one receiving openingformed in said housing; at least one spring disposed in said receivingopening; and at least one cam attached to a shaft disposed adjacent tosaid housing, said cam being disposed adjacent to said opening forextending said spring at a predetermined rotational angle of said shaft,thereby allowing an electrical wire to be inserted into said spring atsaid predetermined rotational angle, and allowing said electrical wireto be compressively trapped in said spring and connected to said wireconnector at other rotational angles of said shaft.
 13. A testingapparatus for testing components of a disk drive including a magnetichead that interacts with a magnetic disk comprising:first translationalmeans linearly slidable in a first direction substantially parallel tothe surface of said magnetic disk; second translational means linearlyslidable in a second direction substantially vertical to the surface ofsaid magnetic disk, said second translational means having said magnetichead attached thereto; and a rotatable arm having a proximal end and adistal end, said proximal end of said arm being rotatably connected tosaid first translational means, said second translational means beingslidably connected to said distal end of said arm; wherein duringtesting, said first translational means linearly slides said rotatablearm along said first direction to a location proximal to said magneticdisk, and said rotatable arm pivotally rotates said second translationalmeans to a predetermined angle above said magnetic disk, therebyallowing said second translational means to adjustably slide saidmagnetic head along said second direction at a predetermined heightabove said magnetic disk.
 14. The testing apparatus as set forth inclaim 13 wherein said first translational means includes a slide andsaid testing apparatus further includes a motor, and a lead screw havingone end rotatably attached to said motor and another end movablyengaging said slide, wherein said first translational means is linearlyslidable by energizing said motor, thereby rotatably actuating said leadscrew which engages and slidably moves said slide along said firstdirection.
 15. The testing apparatus as set forth in claim 13 whereinsaid first translational means includes linear feedback means forallowing said translational means to adjustably move said rotatable armalong said first direction.
 16. The testing apparatus as set forth inclaim 15 wherein said linear feedback means includes an opticalinterferometer.
 17. The testing apparatus as set forth in claim 13wherein said rotatable arm includes rotational feedback means forallowing said rotatable arm to adjustably rotate said magnetic headabove said magnetic disk.
 18. The testing apparatus as set forth inclaim 17 wherein said rotational feedback means includes an opticalinterferometer.
 19. The testing apparatus as set forth in claim 13wherein said second translational means includes linear feedback meansfor allowing said second translational means to adjustably move saidmagnetic head above said magnetic disk along said second direction. 20.The testing apparatus as set forth in claim 19 wherein said linearfeedback means includes a capacitance sensor.
 21. The testing apparatusas set forth in claim 13 further comprising a detachable modulereleasably attached to said second translational means, wherein saidmagnetic head is attached to the second translational means via saiddetachable module which includes a module base; a magnetic head transfermount having said magnetic head attached thereto and disposed on saidmodule base; and an amplifier circuit proximally disposed adjacent tosaid transfer mount on said module base.
 22. The testing apparatus asset forth in claim 21 wherein said amplifier circuit comprises a writedata circuit which includes a multiplier, and a current driver havinginput terminals connected to said multiplier and output terminalsconnected to said magnetic head.
 23. The testing apparatus as set forthin claim 22 wherein said current driver comprises:a differentialamplifier having an assertive circuit portion and a complementarycircuit portion; a bridging circuit connected between said assertive andcomplementary circuit portions; and first and second current sourcescoupled to said assertive and complementary circuit portionsrespectively, such that current from said current sources flows intosaid circuit portions proportionally through said bridging circuit. 24.The testing apparatus as set forth in claim 22 wherein said currentdriver includes a feedback circuit connected thereto for signalstabilization.
 25. The testing apparatus as set forth in claim 22wherein said amplifier circuit comprises at least one data read circuitincluding a variable gain amplifier.
 26. The testing apparatus as setforth in claim 13 wherein said detachable module includes a wireconnector which comprises:a housing; at least one receiving openingformed in said housing; at least one spring disposed in said receivingopening; and at least one cam attached to a shaft disposed adjacent tosaid housing, said cam being disposed adjacent to said opening forengaging said spring.
 27. A testing apparatus for testing components ofa disk drive including a magnetic head that interacts with a magneticdisk comprising:a rotatable arm having a distal end and a proximal end,said proximal end being pivotally connected to said apparatus; avertical slide slidably attached to said distal end of said rotatablearm, said vertical slide being slidable in a direction substantiallyvertical to the surface of said magnetic disk; sensing means attached tosaid vertical slide; and feedback means connected to said sensing means;wherein during testing, said sensing means interacts with the surface ofsaid magnetic disk and sends signals to said feedback means, therebyallowing said feedback means to adjustably slide said vertical slidealong said vertical direction above the surface of said magnetic disk.28. The testing apparatus as set forth in claim 27 comprising anamplifier circuit attached to said vertical slide, said amplifiercircuit comprising:a write data circuit having a multiplier; and acurrent driver having input terminals connected to said multiplier andoutput terminals connected to said magnetic head.
 29. The testingapparatus as set forth in claim 28 wherein said current drivercomprises:a differential amplifier having an assertive circuit portionand a complementary circuit portion; a bridging circuit connectedbetween said assertive and complementary circuit portions; and first andsecond current sources coupled to said assertive and complementarycircuit portions respectively, such that current from said currentsources flows into said circuit portions proportionally through saidbridging circuit.
 30. The testing apparatus as set forth in claim 27further comprising a detachable module having a module base, releasablyattached to said vertical slide, said magnetic head being releasablyattached to said module base, and an amplifier circuit proximallydisposed adjacent to said magnetic head on said module base.
 31. Thetesting apparatus as set forth in claim 30 wherein said detachablemodule includes a pair of hand grips resiliently attached thereto, saiddetachable module being releasably attached to said vertical slide viasaid hand grips gripping said vertical slide.
 32. The testing apparatusas set forth in claim 27 wherein said rotatable arm includes acounterweight attached to said proximal end of said arm.
 33. A testingapparatus for testing components of a disk drive including a magnetichead that interacts with a magnetic disk which includes a plurality ofconcentric data tracks, said apparatus comprising: a base;atranslational slide disposed above said base, said translational slidebeing linearly movable in a first direction substantially parallel tothe surface of said magnetic disk; a rotatable arm having a distal endand a proximal end, said proximal end of said arm being rotatablyattached to said translational slide; and a vertical slide having saidmagnetic head attached thereto, said vertical slide being slidablyattached to said distal end of said rotatable arm, and movable in asecond direction substantially vertical to the surface of said magneticdisk; wherein said translational slide, said rotatable arm and saidvertical slide are operationally movable above said base, such thatduring testing, said translational slide linearly moves said rotatablearm along said first direction to a location proximal to said magneticdisk, and said rotatable arm pivotally rotates said vertical slide to apredetermined location above said magnetic disk, thereby allowing saidvertical slide to adjustably move said magnetic head above thepredetermined location along said second direction.
 34. The testingapparatus as set forth in claim 33 wherein said translational slideincludes a first optical interferometer, said rotatable arm includes asecond optical interferometer, and said vertical slide includes acapacitance sensor.
 35. The testing apparatus as set forth in claim 34including a computer having an interface data bus, wherein said opticalinterferometers and said capacitance sensor electrically communicatewith said computer via said interface data bus.
 36. The testingapparatus as set forth in claim 35 comprising an amplifier circuitdisposed adjacent to the vertical slide, wherein said amplifier circuitelectrically communicates with said computer via said interface databus, said amplifier circuit including:a write data circuit having amultiplier; and a current driver having input terminals connected tosaid multiplier and output terminals connected to said magnetic head.37. The testing apparatus as set forth in claim 36 wherein said currentdriver in said amplifier circuit comprises:a differential amplifierhaving an assertive circuit portion and a complementary circuit portion;a bridging circuit connected between said assertive and complementarycircuit portions; and first and second current sources coupled to saidassertive and complementary circuit portions respectively, such thatcurrent from said current sources flows into said circuit portionsproportionally through said bridging circuit.
 38. The testing apparatusas set forth in claim 37 comprising a detachable module releasablyattached to said vertical slide, said detachable module including modulebase, a magnetic head transfer mount having said magnetic head attachedthereto, said amplifier circuit being proximally disposed adjacent tosaid transfer mount on said module base.
 39. The testing apparatus asset forth in claim 38 wherein said detachable module includes a wireconnector which comprises:a housing; at least one receiving openingformed in said housing; at least one spring disposed in said receivingopening; and at least one cam attached to a shaft disposed adjacent tosaid housing, said cam being disposed adjacent said opening forextending said spring at a predetermined rotational angle of said shaft,thereby allowing an electrical wire to be inserted into said spring atsaid predetermined rotational angle, and allowing the electrical wire tobe compressively connected to said spring in said wire connector atother rotational angles of said shaft.
 40. The testing apparatus as setforth in claim 38 wherein said detachable module includes a pair of handgrips resiliently attached thereto, said detachable module beingreleasably attached to said vertical slide via said hand grips securingsaid vertical slide.
 41. A method of testing a disk drive including amagnetic head that interacts with a magnetic disk having a plurality ofconcentric data tracks registered thereon, wherein on each data track,the magnetic head spaces from the center of the data track at a radialdistance and forms a skew angle with the tangent line to the data track,said method comprising the steps of:disposing a translational slideabove a stationary base and spaced from the magnetic disk; providing arotatable arm having a proximal end pivotally connected to saidtranslational slide, and a distal end connected to the magnetic head;deriving a first mathematical function defining a translational distanceas a function of the skew angle, the radial distance and the geometricalrelationships of said slide and said arm with respect to the magneticdisk; deriving a second mathematical function defining a rotationalangle as a function of the skew angle, the radial distance and thegeometrical relationship of said slide and said arm with respect to themagnetic disk; calculating said translational distance; calculating saidrotational angle; sliding said first translational slide through saidtranslational distance along a longitudinal direction; rotating themagnetic head at said rotational angle; and conducting a test of saidmagnetic head that interacts with the magnetic disk.
 42. The method oftesting as set forth in claim 41 wherein said steps of calculating saidtranslational distance and said rotational angle are performed by acomputer.
 43. A method of testing disk drive components including amagnetic head that interacts with a magnetic disk which includes aplurality of concentric data tracks registered thereon, said methodcomprising the steps of:(a) slidably mounting a first translationalslide linearly movable in a horizontal direction above a stationarybase; (b) providing a rotatable arm having a proximal end and a distalend; (c) pivotally attaching the proximal end of said rotatable arm onsaid first translational slide; (d) slidably mounting a secondtranslational slide linearly movable in a vertical direction to saiddistal end of said rotatable arm, said second translational slide havingsaid magnetic head attached thereto; (e) sliding said firsttranslational slide along said horizontal direction such that saidrotatable arm is disposed adjacent to said magnetic disk; (f)positioning said magnetic head above one of the data tracks registeredon said magnetic disk by rotating said rotatable arm; and (g) slidingsaid second translational means in said vertical direction such thatsaid magnetic head is disposed at a predetermined height above saidmagnetic disk.
 44. The method of testing as set forth in claim 43wherein on each data track, the magnetic head spaces from the center ofthe data track at a radial distance and forms a skew angle with thetangent line to the data track, and wherein step (e) further includesthe sub-steps of:(i) deriving a first mathematical function defining atranslational distance as a function of the skew angle, the radialdistance and the geometrical relationships of said slide and said armwith respect to the magnetic disk; (ii) calculating said translationaldistance; and (iii) sliding said first translational slide through saidtranslational distance along said horizontal distance.
 45. The method oftesting as set forth in claim 44 wherein step (f) further includes thesub-steps of:(i) deriving a second mathematical function defining arotational angle as a function of the skew angle, the radial distanceand the geometrical relationships of said slide and said arm withrespect to the magnetic disk; (ii) calculating said rotational angle;and (iii) rotating said rotatable arm through said rotational angle.